The influence of cannabis use expectancies on cannabis use and psychotic symptoms in psychosis.

INTRODUCTION AND AIMS

Little is known about motives or expectancies for cannabis use in psychotic populations, despite these cognitive factors being a central focus of the treatment for substance misuse in psychosis. This study examined the relationship between cannabis use expectancies, cannabis use and psychotic symptoms among cannabis using psychotic inpatients. A secondary aim was to determine if there were significant differences in the cannabis use expectancies of psychotic patients with and without Diagnostic and Statistical Manual version IV (DSM-IV) cannabis dependence.

DESIGN AND METHODS

Participants consisted of 101 in-patients with psychosis who had used cannabis more than five times in the past year. Expectancies were assessed using the Cannabis Expectancy Questionnaire (CEQ). The frequency of cannabis use, severity of cannabis dependence, presence of DSM-IV cannabis dependence and severity of psychotic symptoms were also assessed using standardised measures.

RESULTS AND CONCLUSIONS

Results suggested that cannabis use expectancies were associated with cannabis use but not symptom variables. Expectancies for cannabis use predicted recent cannabis use and the presence and severity of cannabis dependence. Psychotic patients with DSM-IV cannabis dependence had significantly higher expectancies for negative effects from cannabis use. Prospective research examining the influence of motives and expectancies for cannabis use on cannabis use and psychotic symptoms is required to obtain a greater understanding of substance use in psychosis and assist with the development of innovative treatment interventions.